Fate/stay night, and Fate/hollow ataraxia are directly related, taking place in the same universe. The prequel work "Fate/Zero", while telling the story of the Fourth Holy Grail War 10 years prior to Fate/stay night, is treated as taking place in a very similar parallel world due to various differences in minor details and events. Fate/kaleid liner PRISMA☆ILLYA is a direct spin-off of Fate/stay night featuring characters from Fate/stay night, Fate/hollow ataraxia and Fate/Zero in a parallel world where the Fourth Holy Grail War was stopped before taking place.